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Identification of the Horseshoe Crab
Horseshoe crabs are arthropods and they are distantly related to scorpions and spiders. There are four species of horseshoe crabs with natural habitats in the Atlantic Ocean, the Gulf of Mexico, the Indo-West Pacific region and the South China Sea. Horseshoe crabs live predominately in the bottom of shallow waters preferring to rest, hide and hunt upon the sand or mud. The body of the horseshoe crab includes a hard shell, 10 legs and a long spiked tail that is used for digging and to help flip the animal over if it gets stuck upside down. Horseshoe crabs can live well into their late teens, and their main predators are humans, seabirds and turtles.
Horseshoe Crab Diet
The horseshoe crab is an omnivorous animal, and its main diet consists of small clams, mollusks, worms and seaweed. The horseshoe crab will also eat carrion (dead animals or dead animal remains). All of these foods are found in the horseshoe crab's habitat, and the horseshoe crab will feed on foods found on the surface of the sand or mud or it will use its spiked tail to help dig below the surface to uncover tasty clams and mollusks.
In an aquarium, the horseshoe crab should be fed a diet of dried seaweed and fish food. The Aquatic Connection also recommends supplementing the horseshoe crab diet with bits of squid and shrimp.
Feeding Times
Horseshoe crabs do not begin eating until after they become juveniles. When a horseshoe crab hatches from the egg, it is in a larval stage; approximately 20 days after hatching, the larvae will molt into the first juvenile stage. Juveniles tend to hide during the day, burrowed into the sand or mud, and they come out at night to feed. As the juvenile crabs mature, molt and grow, they will begin to spend more time out during the day. Adult horseshoe crabs spend most of their time during the day looking for food and eating. It can take approximately 10 years before a horseshoe crab reaches full maturity.
How a Horseshoe Crab Eats
The horseshoe crab does not have jaws or teeth. Instead, the horseshoe crab must grind and pulverize food before the food can enter the mouth. The horseshoe crab uses specialized appendages called chelicerae to feel around the sand or mud for food. Once food is found, the food is picked up with the horseshoe crab's claws and then it is pushed towards the legs. On the legs are small but sharp bristles called gnathobases; as the crab moves with its food, the food is passed down the legs to the mouth and on the way it is further broken down by the gnathobases. Then the crab uses the legs near the mouth to push the food bits into its mouth.